Animated display calibration method and apparatus

ABSTRACT

A method for adjusting properties of a display includes displaying a first pluge image on the display to a user, wherein the display includes a plurality of locations, wherein the first pluge image comprises a first plurality of output values associated with the plurality of locations, thereafter displaying a second pluge image on the display to the user, wherein the second pluge image comprises a second plurality of output values associated with the plurality of locations, wherein the first plurality of output values are different from the second plurality of output values, and receiving a display adjustment input from the user, wherein the display adjustment input from the user is in response to the user viewing the first pluge image on the display and in response to the second pluge image on the display.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.11/370,262 filed Mar. 2, 2006, now U.S. Pat. No. 7,760,231 issued Jul.20, 2010, which application claims the benefit of U.S. ProvisionalApplication No. 60/660,216 filed Mar. 9, 2005, each of which are herebyincorporated by reference for all purposes.

BACKGROUND

The present invention relates to optical display calibration methods andapparatus. More particularly, the present invention relates to noveldisplay calibration test patterns and methods of use. Applications maybe applied to displays of any type of media, such as computer animatedmedia.

Throughout the years, movie makers have often tried to tell storiesinvolving make-believe creatures, far away places, and fantastic things.To do so, they have often relied on animation techniques to bring themake-believe to “life.” Two of the major paths in animation havetraditionally included drawing-based animation techniques and stopmotion animation techniques.

Drawing-based animation techniques were refined in the twentiethcentury, by movie makers such as Walt Disney and used in movies such as“Snow White and the Seven Dwarfs” (1937) and “Fantasia” (1940). Thisanimation technique typically required artists to hand-draw (or paint)animated images onto a transparent media or cels. After painting, eachcel would then be captured or recorded onto film as one or more framesin a movie.

Stop motion-based animation techniques typically required theconstruction of miniature sets, props, and characters. The filmmakerswould construct the sets, add props, and position the miniaturecharacters in a pose. After the animator was happy with how everythingwas arranged, one or more frames of film would be taken of that specificarrangement. Stop motion animation techniques were developed by moviemakers such as Willis O'Brien for movies such as “King Kong” (1933).Subsequently, these techniques were refined by animators such as RayHarryhausen for movies including “Mighty Joe Young” (1948) and “Clash ofthe Titans” (1981).

With the wide-spread availability of computers in the later part of thetwentieth century, animators began to rely upon computers to assist inthe animation process. This included using computers to facilitatedrawing-based animation, for example, by painting images, by generatingin-between images (“tweening”), and the like. This also included usingcomputers to augment stop motion animation techniques. For example,physical models could be represented by virtual models in computermemory, and manipulated.

One of the pioneering companies in the computer-aided animation (CA)industry was Pixar. Pixar is more widely known as Pixar AnimationStudios, the creators of animated features such as “Toy Story” (1995)and “Toy Story 2” (1999), “A Bugs Life” (1998), “Monsters, Inc.” (2001),“Finding Nemo” (2003), “The Incredibles” (2004), and others. In additionto creating animated features, Pixar developed computing platformsspecially designed for CA, and CA software now known as RenderMan®.RenderMan® was particularly well received in the animation industry andrecognized with two Academy Awards®. The RenderMan® software included a“rendering engine” that “rendered” or converted geometric and/ormathematical descriptions of objects into a two dimensional image.Images are then recorded to a media such as film, DVD, or the like, forlater viewing.

To display the rendered and recorded images to viewers (e.g., audience,users) in a manner contemplated by the director, display devices need tobe properly tuned or calibrated. Some types of calibration include blacklevel adjustment, white level adjustment, gamma correction, contrastadjustment and the like. In the past, methods for optically calibratingdisplays have typically relied upon static calibration images.Specifically, a calibration image would be displayed on a displaydevice, and based upon how the image appeared on the display device, auser would adjust the brightness, contrast, and the like of the displaydevice. Alternatively, a user would adjust a display driver until thecalibration image appeared “correct” to the viewer.

The inventor of the present invention has determined that the ability ofusers to correctly judge or determine when the calibration imageappeared “correct” was often difficult, in part, because of the wayhumans detect changes in luminance values. More specifically, theinventor realized that with static images, it is difficult for a humanto determine whether two similar shades of gray, for example, appeardifferent when displayed.

The inventor also realized that conventional DVD players are unable toreliably display variations in gray scale of less than approximately3.9%, due to quantization effects of the data coding and data decodingprocess. Because of these quantization approximations for typicaldisplay driving devices, previously one could not readily calibratedisplays to a high degree of accuracy.

Additionally, the inventor of the present invention has also determinedthat although some dedicated display calibration software may have beenavailable, such software was not widely used. One reason was that theywere typically stand-alone software packages that a user would have tospecifically purchase. Another reason was that they included a number ofseparate tests for each parameter to be adjusted and requires a user torun a large number of individual tests to calibrate a display. This wasalso very burdensome, thus consumers were not performing suchcalibrations. For these reasons, and others, such packages do not appearto be widely used by consumers.

Accordingly, what is desired are improved methods for presentingcalibration data to users to facilitate the calibration of displaydevices.

BRIEF SUMMARY

The present invention relates to optical display calibration methods andapparatus. More particularly, the present invention relates to noveldisplay calibration test patterns and methods of use.

The herein described techniques and display are designed to give usersthe ability to match settings of the display equipment to settings usedduring production of a feature/content. This allows users to experiencea feature how the director originally intended the content to be seen.

Through the use of various embodiments of the test patterns describedherein, a user may adjust the display equipment settings for highfidelity playback. In some cases, these settings enhance details in theshadows, as well as areas with high levels of luminance (i.e., theamount of light in the picture. Additionally, in some embodiments,proper display settings will produce a picture with subtle detail inboth dark and light areas. Additionally, in some embodiments, afteradjustment, the entire range of the picture, from the darkest to thebrightest areas of the image should be observable.

Embodiments of the present invention include novel test patterns thathelp uses users modify a display monitor's contrast and brightnesssettings. The display equipment monitor may include rear-projection,front-projection, DLP, LCD, CRT, plasma, or other type of display.

In specific embodiments, a single set of test patterns allows the userto optimize the black level. As will be illustrated below, a BlackOptimize portion of the set of test patterns allows a user to optimizethe display of the blacks in the picture, thereby enabling the displayof rich shadows, without the loss of detail. The set of test patternshave different gray levels, thereby appearing to blink on and off,making the difference easier for a user to see. In various embodiments,a center bar of the Black Optimize pattern may be the same shade ofblack as the background of the test pattern. In various configurations,the center bar may be the “darkest” black that the monitor will display.

In various configurations, the four bars on the left portion of theBlack Optimize portion of the test pattern, encompass four shades ofintensity darker than the “darkest” black. Meanwhile, the four bars onthe right portion of the test pattern, encompass four shades lighterthan the “darkest” black. Ideally, if a monitor or projector is properlycalibrated, the four bars on the left should not be visible while thefour bars on the right should be visible as the pattern blinks on andoff.

Depending on the capabilities of a DVD player, the monitor or projector,or the like, shades darker than the “darkest” black may not be visible.Some audio/video components cannot play back video levels below the“darkest” black that is found in the background of this test pattern. Invarious embodiments, shades darker than the “darkest” are sometimestermed “super-black.”

In various embodiments, a similar structure may be provided for thewhite levels. In particular, a number of arrears in the set of testpatterns may alternatively blink between the “whitest” white and valuesless than the “whitest” white, and between the “whitest” white and“super-white.” Again, the user may adjust the brightness until“super-white” regions are not perceptible.

In specific embodiments, the single set of test patterns allows the userto optimize the gamma level. As will be illustrated below, the gammaoptimization portion of the test patterns includes “ramps” and “blocks.”In one embodiment, the ramps are represented by twelve columns thatappear from left to right on the screen. Further, in each column, eachramp is made up of alternating horizontal lines of black and aparticular shade of gray. In one specific embodiment, in the set of testpatterns, one test pattern begins with a black horizontal line, a grayline, a black line, etc; and the next test pattern begins with a grayhorizontal line, a black line, a gray line, etc.

In one embodiment, the blocks are represented as squares of uniform grayscale intensity that appear within each Ramp from the top to the bottomon the screen. The shade of gray is the same within each Ramp from topto bottom, but varies in luminance for each Ramp from left to right.

In various embodiments, the shades of gray found in the ramps and blockshelp the user determine the ability of the system to display variousluminance levels simultaneously. The combination of the ramps and blocksin the set of test patterns can be viewed by the user for adjustingContrast and/or Gamma (if supported). Additional the ramps and blocksallow a user to set parameters for other possible settings such as“Cinema,” “Sport,” and other modes.

In some embodiments of the present invention, the ramps and blocksappearing in the set of test patterns may be the same. Accordingly, theuser may view the ramps and blocks by squinting, viewing through a pinhole aperture, or the like. By doing so, the user should see thehorizontal lines in each Ramp blur together to foam a solid gray shade,producing 12 solid vertical bars, each of which has several Blockswithin it. The gray Blocks will typically appear to be depressed withinthe Ramp, raised outwards from the Ramp, or the same shade as the Ramp.The user may then adjust the Contrast and/or Gamma adjustments until theappearance of the blocks and the ramps blur together.

In some embodiments of the present invention, a zone plate is alsoprovided that moves over the set of test patterns. In variousembodiments, the zone plates help to illustrate aliasing artifacts anddeinterlacing artifacts to users. Additionally, in other embodiments,the quality of appearance of the zone plates depends upon the type ofinterconnection between the video player device and the display device.For example, the color appearance of the zone plates of a system usingS-video or component video connections may be inferior to the appearanceof the zone plates of a system using HDMI, DVI, or the like connections,a Faroudj a driver, or the like.

Embodiments of the present invention may be applied to virtually anydisplay device, such as DLP displays (DLP projectors and reflectivescreens or transmissive screens), LCD displays, CRT displays, plasmadisplays, front or rear projection displays, OLED displays, LCoSdisplays, computer monitors, or the like. An example of a DLP projectormay include a theater DLP projector and a theater screen. Additionally,embodiments may include any number of display driver hardware includingDVD players, computer video cards (e.g. GPU), VCR, personal videorecorders (PVRs) (e.g., TiVo), or the like.

Various embodiments of the present invention include animated displaycalibration patterns. More specifically, embodiments are directed toanimate picture line-up generator patterns (Pluge patterns), tofacilitate the adjustment of black-level and white-level characteristicsof a display with an accuracy previously unobtainable. Additionalembodiments are directed to animate ramp patterns, to facilitate theadjustment of contrast and/or gamma characteristics of a display.Additional embodiments are directed to a single set of display imagesthat allow a user to adjust brightness, contrast, and/or gamma within asingle view.

According to one aspect of the invention, a method for a display isdisclosed. One process may include outputting a first display image fromthe display for at least one display frame time, wherein the firstdisplay image comprises a first portion including a first set ofintensity values in a first pattern and a second portion including asecond set of intensity values in a second pattern. A technique mayinclude outputting a second display image from the display for at leastone display frame time, wherein the second display image comprises afirst portion including a third set of intensity values in the firstpattern and a second portion including the second set of intensityvalues in the second pattern, wherein the display displays a temporallycomposite image in response to first display image and in response tothe second display image, wherein the composite image includes a firstregion comprising a combination of the first set of intensity values ofthe first display image in the first pattern and the third set ofintensity values of the second display image in the first pattern, andcomprising a second region comprising the second set of intensity valuesin the second pattern, wherein the temporally composite image issubstantially flicker-free. Additionally, a process includes receiving adisplay control signal for the display from a user in response a visualcomparison of intensity values of the first region in the compositeimage on the display compared to intensity values of the second regionin the composite image on the display.

According to another aspect of the invention, a display driving deviceis disclosed. One apparatus may include a memory configured to store arepresentation of a first display image and a representation of a seconddisplay image. One system may include a processor coupled to the memory,wherein the processor is configured to output the first display image toa display device for a first number of display frames in response to therepresentation of the first display image, and wherein the processor isconfigured to output the second display image to the display device forthe first number of display frames in response to the representation ofthe second display image. In various embodiments, the first displayimage comprises a first portion including a first set of intensityvalues in a first pattern and a second portion including a second set ofintensity values in a second pattern, wherein the second display imagecomprises a first portion including a third set of intensity values inthe first pattern and a second portion including the second set ofintensity values in the second pattern, wherein the display devicedisplays a temporally composite image in response to the first displayimage and in response to the second display image. In variousembodiments, the composite image includes a first region comprising atemporal combination of the first set of intensity values of the firstdisplay image in the first pattern and the third set of intensity valuesof the second display image in the first pattern, and comprising asecond region comprising the second set of intensity values in thesecond pattern, wherein the temporally composite image is substantiallyflicker-free. Additionally, in various embodiments, the visualcharacteristics of the display device are adjusted by a user in responsea visual comparison by the user of intensity values of the first regionin the composite image on the display compared to intensity values ofthe second region in the composite image on the display.

According to another aspect of the invention, a method for adjustingproperties of a display is described. One process includes displaying afirst image on the display to a user, wherein the display includes aplurality of locations, wherein the first image comprises a firstplurality of output values associated with the plurality of locations,and thereafter displaying a second image on the display to the user,wherein the second image comprises a second plurality of output valuesassociated with the plurality of locations, wherein the first pluralityof output values are different from the second plurality of outputvalues by approximately 1%, or less. Additional methods may includereceiving a display adjustment input from the user, wherein the displayadjustment input from the user is in response to the user viewing thefirst image on the display and in response to the second image on thedisplay.

According to yet another aspect of the invention, an apparatus isdescribed. One system includes a display device configured to display afirst image and a second image, wherein the display device is configuredto allow a user to adjust display parameters, wherein the displayincludes a plurality of locations. One apparatus includes a displaydriving device coupled to the display device, wherein the displaydriving device is configured to provide the first image to the displaydevice, wherein when the first image is output on the display device,the plurality of locations are associated with a first plurality ofdisplay values, wherein the display driving device is also configured toprovide the second image to the display device, wherein when the secondimage is output on the display device, the plurality of locations areassociated with a second plurality of display values, and wherein adisplay value from the first plurality of display values for the firstimage is different from a display value from the second plurality ofdisplay values for the second image by approximately 1%, or less. Invarious embodiments, the user adjusts the display parameters in responseto the first image displayed on the display device and in response tothe second image displayed on the display device.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more fully understand the present invention, reference ismade to the accompanying drawings. Understanding that these drawings arenot to be considered limitations in the scope of the invention, thepresently described embodiments and the presently understood best modeof the invention are described with additional detail through use of theaccompanying drawings in which:

FIG. 1 illustrates a static calibration display indicating a series oftest calibration regions;

FIGS. 2 and 3 illustrate an embodiment of the present invention;

FIG. 4 illustrates an example of a display supporting super-blackfunctionality;

FIG. 5 illustrates another embodiment of the present invention;

FIGS. 6 and 7 illustrate portions of other embodiments of the presentinvention;

FIG. 8 illustrates another embodiment of the present invention.

FIG. 9 illustrates an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 illustrates a static calibration display 100 indicating a seriesof test calibration regions. As annotated in FIG. 1, the regions includea region 110 adapted to be used for calibrating a display black level; aregion 120 adapted to be used for calibrating a display white clippinglevel; and regions 130 including ramps 140 and blocks 150 adapted to beused for calibrating a display gamma value. Static calibration display100 is not within the prior art, and is referenced for purposes ofterminology and understanding.

In the embodiment in FIG. 1, black optimize region 110 includes ninesub-regions (e.g., columns) of interest, however in other embodiments, agreater or lesser number of sub-regions are provided or are of interest.Additionally, in the example in FIG. 1, white check region 120 includeseight sub-regions (e.g., equally sized squares) of interest, however inother embodiments, a greater or fewer number of sub-regions can be usedor are of interest. In various embodiments, the shapes of region 110 andregion 120 may be changed. For example, the step-type patterns of region110 may be replaced with a series of adjacent or separatedidentically-shaped rectangles, squares, circles, or the like. As anotherexample, region 120 may be embodied as a series of eightidentically-sized squares, a series of identically-shaped rectangles,may be presented as a series of separated or adjacent shapes such astriangles, ovals, or the like.

Similar to the above, the number and arrangement of ramps 140 and blocks150 in regions 130 may vary from the embodiment illustrated in FIG. 1.For example, blocks 150 may be other shapes such as rectangles, plussigns, circles, ovals, or the like. Additionally, ramps 140 may have agray-scale ramp appearance from left-to-right as illustrated, may beramped top-to-bottom, may include a ramp-up and ramp-down fromright-to-left, and/or top-to-bottom, and the like. Ramps 140 may also beshaped as squares, rectangles, triangles, ovals, or other shapes.

Additionally, the arrangement of the regions may be different. Forexample, region 120 or region 110 may be in the center of display 100,near an edge, or the like. The regions may also be duplicated on adisplay. For example, more than one black optimize region 110 and/orwhite check region 120 may be on the display at one time, such as, onopposite diagonal corners, and the like. In still other embodiments,less than all of the regions may be displayed on the display at the sametime. As examples: black optimize region 110 and white check region 120may be on one image; region 130 and region 120 may be on another image;region 110 and region 130 may be on a third image, or the like.Accordingly, in various embodiments, regions 110, 120 and 130 may bepresented together within one or more images, and in other embodiments,regions 110 and 120; and 130 may be displayed to the user in separatescreens, or may be displayed in various combinations.

In light of the above, one of ordinary skill in the art will recognizethe configuration of regions in FIG. 1 is merely one of many possibleconfigurations. Accordingly, the configurations illustrated are notnecessarily limiting as to the scope of patent protection.

In various embodiments of the present invention, a scale from 0 to 1 isused to represent intensity values. In other embodiments values from 0to 255, or others are can also be used. In practice displayable valueson a display range from approximately 0.1 to 0.9, with values fromapproximately 0 to 0.1 (0 to 16/255) termed “super black” values andfrom approximately 0.9 to 1 (230 to 255/255) termed “super white”values. Typically, super black and super white values should not bediscernable on a properly calibrated display.

FIGS. 2 and 3 illustrate a set of calibration images used to drive adisplay. More particularly, FIGS. 2 and 3 illustrate calibration imagesthat are repeatedly displayed to a user on the display device. Theexample in FIG. 2 illustrates a first state (image) 200 for thecalibration regions to be displayed on a display device, and FIG. 3illustrates a second state (image) 300 for the calibration regions to bedisplayed on the display device. With such embodiments, as can be seen,the intensity values in first image 200 and second image 300 aredifferent. Accordingly, when successively output to the user, theregions of the respective images that change in intensity appear to auser to be animated (i.e., blink).

FIG. 2 illustrates an example of a first configuration of a black levelregion 220. In FIG. 2, a middle column 225 is set to represent a blacklevel of 0.1, or the like. Middle column 225 thus represents a region ofa display that has the darkest black to be displayed on the display. Inthe example in FIG. 2, the left four columns 230 and the right fourcolumns 240 may also be set to black level 0.1 in first image 200.

A first configuration of a white level region 260 illustrated in FIG. 2.In this specific example, white check region 260 includes shapes havingintensity values that may be less than the maximum value or the whitestwhite (e.g. 0.9). In the embodiment shown, eight squares are provided inFIG. 2 having different intensity values. For example, the eight squaresmay have variations from the whitest white such as: −4%, −3%, −2%, −1%,+1%, +2%, +3%, +4%, and the like. As an example, white check region 260may have values (right to left, top to bottom): 0.9, 0.891, 0.882, 0.9,0.873, 0.9, 0.9, 0.864.

FIG. 3 illustrates an example of a second configuration of a black levelregion 320. In FIG. 3, a middle column 325 may also represent a blacklevel of 0.1, or the like similar to middle column 225. In the examplein FIG. 3, the left four columns 330 are set to values less than zero,within the “super-black,” if supported by the display driving device.Super-black capability is currently provided by some DVD players, or thelike, and supported by some displays (e.g., DLPs). For example, the leftfour columns may have values such as 0.096, 0.097, 0.098, 0.099 or thelike. See FIG. 4 for an embodiment where the display driver does notsupport super-black. As shown, the left four bars are indistinguishablein intensity from the background black. See FIG. 5 for an embodimentwhere the display driver supports super-black. As can be seen, the leftfour bars should be distinguishable in intensity from the backgroundblack.

In various embodiments, the right four columns 340 are typically set toblack levels greater than zero. For example, the right four columns mayhave values such as 0.101, 0.102, 0.103, 0.104 or the like.

A second configuration 350 of a white level region 360 illustrated inFIG. 3. In this specific example, white check region 360 includessimilar shapes to white check region 260, and have has intensity valuesthat may be less than the maximum value or the whitest white. Theintensity values for the shapes in white check region 360 should bedifferent from those in white check region 260. As an example, whitecheck region 360 may have values (right to left, top to bottom): 0.891,0.9, 0.9, 0.882, 0.9, 0.873, 0.864, 0.9.

In operation, Black Optimize regions 220 and 320 provide the user withvisual feedback for optimizing the black level appearance on a displaydevice. Proper black level calibration enables the display device todisplay rich shadows without loss of detail, for example. In the presentembodiment, a display device is repeatedly driven with firstconfiguration 220 and second configuration 320. For example, five framesof first configuration 220, five frames of second configuration 320,five frames of first configuration 220; alternatively firstconfiguration 220 is displayed for a certain amount of time, then secondconfiguration 320 is displayed for a certain amount of time; and thelike

In other examples, additional intensity configurations for the blacklevel regions are contemplated. These additional configurations can alsobe displayed along with first configuration 220 and second configuration230, repeatedly.

In various embodiments of the present invention, because the intensityor gray scale values of the black level region change with eachdifferent configuration, particular regions within the Black optimizeregion will typically appear blinking to a viewer of the display. Asmentioned above, in this embodiment, middle column 225 and 325 have thesame intensity value as the blackest desired black level. Accordingly,the left four columns 330 of middle column 325 appear to successivelydip below black (to super black) and then return to black (230).Additionally, the right four columns 340 of middle column 325 appear tosuccessively rise above the black level (325) and then return to black(240). In various embodiments, the apparent “blinking” rate of the leftor right four columns may freely set from 1 to 2 a second; from 0.5 to 4a second, 0.25 to 10 a second, and the like.

If the black level is correctly set, the viewer should not be able tosee the blinking of the left four columns (e.g., 330). Conversely, ifthe user can see blinking of the left four columns (e.g., 330), the useris instructed that the black level of the display device (or displaydriver) should be decreased. A caveat to the above is that that theblack level should be set such the user should still be able to see theblinking of the right four columns (e.g., 340). In various embodiments,when all four bars on the left side of middle column 320 do not visiblyblink, and all four bars on the right side of middle column 320 dovisibly blink, the black level has been appropriately set. In practicalterms, the user cannot see any black values on the screen darker thanthe desired black level, yet the user can still see black values lighterthan the desired black level.

In operation, the White Check regions are used by a user to confirm thatthe white levels are not being clipped. In the present embodiment,because intensity of gray-scale display driving values for shapes withinfirst configuration 250 and second configuration 260 are different, theWhite Check region also appears to blink to the user. In variousembodiments, White Check allows a user to adjust a display to displaythe full range of highlight information without artifacts. In oneexample, if a user can only see, for example, four out of the eightshapes blinking, this may indicate to the viewer that the dynamic rangeof the display device is too limited, and that the white level must belowered. In various embodiments, brightness, or contrast of a displaymay be adjusted by a viewer until all the desired regions within theWhite Check regions visibly blink. In practical terms, the user can thusvisibly distinguish between very light values (e.g., 0.89) and white(e.g., 0.9).

In various embodiments of the present invention, ramps 140 and blocks150 illustrated in FIG. 1 can be used by a user to properly adjust thegamma of the display device. Although not easily determinable in FIGS. 6and 7, the orientation of ramps 140 and blocks 150 are different. InFIGS. 6 and 7, ramps 140 may be represented by a series of lines ofdifferent intensity, for example the even lines may be lighter inintensity than the odd lines in FIG. 6 and in FIG. 7, the even lines maybe reversed, and the odd lines may be lighter in intensity than the evenlines. In other embodiments, in a first image the first two lines arelight, the next two lines are dark, etc.; and in a second image, thefirst two lines are dark, the next two lines are light, etc. The valuesof the dark and light stripes in ramps 140 can be predetermined usingconventional gamma control images. As above, these two or more imagesfor ramps 140 may alternatively be displayed on the display to the user.Further, additional configurations may also be used.

In various embodiments, display devices are typically progressive scandevices and may have resolutions such as VGA, SVGA, XGA, WXGA, SXGA,UXGA, 1080p, 720p, 480p or the like. In such embodiments, the refreshrate is often 60 frames per second or greater.

In contrast to the black level and the white level discussions, above,it is desirable that the alternating intensities for ramps 140 totemporally average the different intensity values as viewed by a viewer.Merely as an example, a line on the display device may have an intensityof 0.8 (line 610) for a first 0.25 seconds, an intensity of 0.1 (line720) for the next 0.25 seconds, an intensity of 0.8 for the next 0.25seconds, and the like. In such an example, the line appears to have anaverage intensity of approximately 0.45. The temporal averaging may be afeature of the display device or physiology of the eye.

In various embodiments, the value of blocks 150 are pre-determined to bethe average of the high and low values of the ramps surrounding therespective blocks. For example, as illustrated in FIG. 6, line 610 has avalue of 0.8, line 620 has a value of 0.5, line 630 has a value of 0.1,and line 640 has a value of 0.1. Additionally, block 650 has a constantvalue (between the configurations) of approximately 0.45, and block 660has a constant value (between the configurations) of approximately 0.3.

In some embodiments, the user attempts to adjust the gamma values oframps 140 that drive the display (or the display driver) until ramps 140and blocks 150 blend together and have the same apparent luminance for agiven “mode” setting, such as “Cinema,” “Sport,” “Game,” and the like.

FIGS. 6 and 7 illustrate a more detailed portion of a set of calibrationimages. In this example, in FIG. 6, ramps 140 are represented asalternating lines, as shown, and blocks 150 are represented by solidsquare patches. In FIG. 6, a ramp pattern is represented by two lines ofa first intensity, two lines of a second intensity, two lines of a firstintensity, etc. As can be seen lines 630 are immediately above a block,and are dark in intensity. Above that are lines 610 that are lighter inintensity. In FIG. 7, the ramp pattern is also represented by two linesof a first intensity, two lines of a second intensity, two lines of afirst intensity, etc. However, as can be seen lines 710 immediate abovea block are light in intensity. This contrasts to 630, above.

As discussed above, the calibration images in FIGS. 6 and 7 arerepeatedly output to drive the display. The images are thenalternatively displayed to the user (e.g., FIG. 6, FIG. 7, FIG. 6, FIG.7, etc.). To the viewer, the lines above the block are dark 630 for thenext frame, are light 710 for one frame, are dark 630 for one frame,etc. As a result, the values for each line are respective temporalintegrations of the values on that line from the different calibrationimages. In various embodiments of the present invention, when the gammahas been appropriately been adjusted for the display device, the valuesof the blocks and surrounding ramps should not be distinguishable forall blocks. Further, if certain blocks are distinguishable from therespective ramps, the gamma requires further adjustment.

In other embodiments of the present invention, the ramps or blocks mayappear in other geometric configurations such as stripes in a verticaldirection, such as checkerboard patterns, triangular patterns, or thelike. For example, in a checkerboard pattern, for a first calibrationimage, the right top-most square may be light, and for the secondcalibration image, the right top-most square may be dark, etc. In lightof the present disclosure, the inventor believes that many possibledesigns and arrangements of patterns for the ramps or blocks can beenvisioned to one of ordinary skill in the art.

Exemplary techniques for display calibration include:

I) Starting with “Black Optimize.” Turn the “Brightness” (or blacklevel) control up until all nine bars are visible in the Black Optimizeregion. The black level and white level regions may look similar to FIG.4 or 5.

-   -   a) If the bars on the left are visible, the display and display        driver both support “super-black” (e.g., FIG. 5), turn-down the        Brightness, until the left four bars do not visibly blink. In        other words, the four bars should appear as black as the black        background. Ideally, the four bars on the right of the Black        Optimize pattern should remain visibly blinking.    -   b) If bars on the left do not visibly blink, despite the        increased brightness, the display driver does not support        super-black and brightness adjustments may not be made as        accurately. (e.g., in FIG. 4). The brightness should then be        turned down, such that the four blocks on the left remain just        visibly blinking.

In either case a) or b), the Brightness should be then be set correctly,given the setting of all other controls.

Note, after making subsequent adjustments to the display, such as Gammaadjustment (described below), Picture adjustment or specialized “Cinema”controls, the Black Optimize should typically be checked and orrepeated, as necessary.

II) Gamma correction is performed. In this embodiment, looking at theRamps and blocks on the display, a user may use a “Gamma” or “GammaTrim” control in preference to the Contrast control. In variousembodiments, the Contrast (or gamma controls) are adjusted such that theBlocks neither visually “protrude” from nor “recede into” the ramp bars.In other words, the Blocks and the Ramps should have matched intensityfor all ramp/block sets.

III) Check the “White Check” pattern. The viewer then visually checksthe White Check pattern to make sure the blocks are still visiblyblinking. If they have become washed-out and no longer distinguishable,the Contrast or Brightness need to be lowered, and other adjustmentssuch as Picture, Gamma and possibly custom “Cinema/Sport” settings maybe used to compensate for the decrease.

IV) In some embodiments of the present invention, the above steps arerepeated until all three conditions are satisfied.

Specific novel features of embodiments of the present invention arebelieved to include combinations of animated calibration displays and/orincreased output level accuracy.

FIG. 8 illustrates another embodiment of the present invention. In thisembodiment a region 750 (a “White Optimize region”) is adapted to beused for calibrating the display white level. The operation of region750 is similar to the display black level region 110, in FIG. 1. In thisembodiment, center bar 760 may be held at the super white value (e.g.,0.9), and the bars 770 to the left of center bar 760 may also be atsuper white (e.g., 0.9) in a first calibration image, and may be atvarying levels in a second calibration image (e.g., −4%, −3%, −2%, −1%from 0.9). Additionally, the bars 780 to the right of center bar 760 mayalso be at super white (e.g., 0.9) in a first calibration image, and maybe at varying levels in a second calibration image (e.g., +1%, +2%, +3%,+4% from 0.9). Similar to black check region 110, blinking of valuesless than super white should be discernable by a user on the display,whereas super white blinking should not be discernable by a user on aproperly calibrated display.

FIG. 8 also illustrates a zone plate 790. In various embodiments of thepresent invention, zone plate 790 may move about an image and serve as a“magnifying” glass to give a close-up view of portions of thecalibration images. In various embodiments, the set of calibrationimages include calibration images where zone plate 790 moves overdifferent portions of the image. In various embodiments, zone plate 790should be a smoothly moving zone plate pattern. There is not typically a“right answer”, but rather a pattern to assist the user in assessingrelative image and motion quality. With multiple resolutions,deinterlacing or output interfaces for a display and a display driver,the user may compare results while watching tracking this pattern. Invarious embodiments, the motion of the pattern should be smooth, withlittle hitching or stuttering. Additionally, there should be littlevisible horizontal or vertical structure, little color interference,only black and white. In various embodiments, the zone plate allows theuser to see detail across the entire pattern. Typically, it isenvisioned that users will compare the various output and input modes ofa display driver player and monitor or projector, to find a pleasingcombination.

It is typically very difficult to see subtle luminance transitions in astatic image. In traditional “Pluge” (Picture Line-Up Generator)patterns, three bars are output, each of which are approximately 4%different from each other in luminance. Specifically, using 8-bit dataquantization tables, the three bars are typically 1 bit different inintensity (1/256=3.9%). In light of this, typical conventional DVDplayers cannot reliably display gray scale intensity values that areless than approximately 4% apart, such as 3%, 2%, 1%, or the like.

In contrast, in various embodiments of the present invention, the “BlackOptimize” and “White Optimize” patterns drives the display withintensity values that are approximately 0.9% different in luminance fromeach other. Specifically, MPEG/DVD standards specify 10-bit values aremapped to 8 bits values in a process termed quantization. In otherembodiments, the difference in luminance may be varied from about 0.5%to almost 4%. These differences in luminance are very difficult toperceive statically as the user adjusts black (or white), causing thepercentage difference to become extremely small on the left-side of thepattern, as the bars begin to fall below black. Using embodiments of thepresent invention, the differences are astonishingly easy to see withanimation. This is believed so because while the human eye can seeabsolute luminance levels in the true state of scotopic vision (belowapproximately 0.034 cd/m^2), this condition is essentially never met invideo or film reproduction. However, the human eye can perceiveluminance changes in time (i.e., motion) easily, in all lightingconditions, and at both the dark and bright ranges of luminance levels.

The small differences (e.g., 0.9%) in luminance values can also be usedin the White Contrast pattern. Additionally, differences in luminancemay range from approximately 0.5% to almost 4%. As illustrated, thedifferences in luminance alternates (dark->bright switches tobright->dark), and in some embodiments, alternates are presented(flopped) next to each other to maximize simultaneous contrast.

In various embodiments the animation rate for the “black optimize”pattern and the “white optimize” pattern must be carefully chosen tofall well outside the flicker-fusion range, yet still be fast enough tostimulate the change-sensation in the eye. In one embodiment of thepresent invention, the patterns switch at a rate of about 4 Hz, but maybe different in other embodiments, such as 1 Hz, 0.5 Hz, or the like. Incontrast, for the “gamma” pattern, fusion of the two or moreconfigurations is desired, accordingly, these patterns may switch at therate of less than 4 Hz, 30 Hz, 60 Hz, or as desired.

In various embodiments, the use of intensity values that are alignedwith DCT blocks and 10-bit DC coefficients improve the luminanceaccuracy. In some embodiments, because the 0.9% luminance encode (e.g.,1, 3, 5 etc.) translates to exactly two bits in the final output, highaccuracy luminance output is desired. In other portions of thecalibration images, specifically the Transfer Optimize Blocks,full-scale 1-bit accuracy is required. The industry currently believesthat 4-bit accuracy is unachievable with inexpensive consumer displaydriving devices (e.g., DVD players). Accordingly, to avoid potentialproblems with round-off, sloppy math calculations, and “chroma bugs”seen in some chipsets, the following process was used to achieve highaccuracy:

a) The calibration patterns that have high accuracy are formed out of8×8 pixel blocks arrayed on an 8×8 grid. In various embodiments, thegrid is defined inside the 720×480 container (720×576 for PAL) withwhich MPEG encoding is done. 720×480 or 720×576 represents current DVDresolution. In other embodiments, higher resolution, such as 1080presolution may also be used. The values of the pixels in each 8×8 pixelblock are set constant. Accordingly, each of these 8×8 pixel blockscorresponds to a single DCT transform coding instance, and thus each ofthese blocks will ideally have zero coefficients for everything exceptfor the DC coefficient (i.e., AC coefficients of “0”). For example, thecoefficients for the 8×8 block is the DC bias, the coefficients for four4×4 sub-blocks are 0; the coefficients for 16 2×2 sub-blocks are 0; thecoefficients for 64 1×1 sub-blocks are also 0. In other words, each 8×8block represents data having a “flat field.”

b) It is possible inside the MPEG-2 encoding method used for DVDs tospecify 10-bits to be used for DC coefficient precision. Accordingly,quantization tables of DVD players, or the like and the variations isoutputs provided by different DVD players are bypassed for DCcoefficients, in various embodiments. Thus, essentially 10-bit accuracyis possible for luminance encoding, thus enabling full and accurate8-bit luminance values to be output to the DACs of the display driver.Accordingly, in various embodiments described above, a 0.9%(1/1024˜=0.1%) difference in luminance values can be achieved for thecalibration patterns illustrated above.

In light of the above, extremely high accuracy test patterns arepossible with modest bit streams.

As discussed above, for gamma calibration, a temporal integrationbetween two or more configuration images can be relied upon. Theseembodiments are implementable on progressive scan displays and playerswithout excessive flickering. In such embodiments, a 60 Hz pattern canbe used, and true temporal fusion may appear to the user. Accordingly,the viewer can more easily make adjustment to the monitor. In practice,these embodiments are quite effective.

In some embodiments, patterns are constructed such that the de-fieldingalgorithms of the DVD player or display essentially pull the fieldsapart into different images. Typically moving horizontal lines isdiscouraged, as most deinterlaces view that as aliasing. Accordingly,the ramp lines are at least two display lines wide. In otherembodiments, alternating vertical stripes of black and the selectedintensity (rather than alternating horizontal lines) can be used thatswap back and forth every 60 Hz. The result is a solid band of truehalf-intensity (in the photon sense) illumination. Depending on thedeinterlacer algorithm, an alternate embodiment creates a checkerboardwhere the gray and black squares trade places every 60th of a second.

FIG. 9 is a block diagram of an embodiment of the present invention.Specifically, a display system 800 is illustrated including a displaydriver 820 coupled to one or more display devices 810. A variety of userinput devices, 830 and 840 may be provided as inputs to display driver820. In one embodiment, a data interface 850 may also be provided.

In various embodiments, display device 810 may be a television ormonitor display such as a CRT display, plasma display, LCD display, OLEDdisplay, or the like. Some common embodiments include home-theaterdisplays, computer displays, and the like. Such displays are sometimestermed user direct-view displays. In various embodiments, display device810 may include a DLP projector, LCD projector, CRT projector, or thelike. Such displays also typically include reflective-type screens whichreflect-back light to a viewer. Some common embodiments may include ahome-theater or a commercial big-screen theater, or the like.Additionally, in various embodiments, display device 810 may be a DLPrear-projection display, an LCoS rear-projection display, a CRTrear-projection display, or other rear-projection display. In suchembodiments, an image is projected onto a back-side of a translucentmedia which is then viewed by a viewer. In some embodiments of thepresent invention, display devices 810 may be non-interlaced,progressive-scan monitors.

In various embodiments, user input device 830 includes wired-connectionssuch as a computer-type keyboard, a computer mouse, a trackball, a trackpad, a joystick, drawing tablet, microphone, and the like; and userinput device 840 includes wireless connections such as wireless remotecontrols (e.g., infrared remote, radio frequency remote), wirelesskeyboards, wireless mice, and the like. In the various embodiments, userinput devices 830-840 typically allow a user to select objects, icons,text and the like that graphically appear on a display device (e.g.,810) via a command such as a click of a button or the like. Otherembodiments of user input devices include includes front-panel buttonson display driver 820.

Embodiments of data interfaces 850 typically include an Ethernet card, amodem (telephone, satellite, cable, ISDN), (asynchronous) digitalsubscriber line (DSL) unit, FireWire interface, USB interface, and thelike. In various embodiments, data interfaces 850 may be coupled to acomputer network, to a FireWire bus, a Satellite cable connection, anoptical cable, a wired-cable connection, or the like. In variousembodiments of the present invention, data interfaces 850 may includeanalog or digital image data to be decoded and output to users viadisplay devices 810. In other embodiments, computer interfaces 850 maybe physically integrated on the motherboard of display driver 820, maybe a software program, such as soft DSL, or the like.

In various embodiments, display driver 820 may include familiarcomputer-type components such as a processor 860, and memory storagedevices, such as a random access memory (RAM) 870, disk drives 880, andsystem bus 890 interconnecting the above components.

In various embodiments, display driver 820 includes a microprocessors ormicrocontroller. Further, in various embodiments, display driver 820typically includes an operating system.

RAM 870 and hard-disk drive 880 are examples of tangible mediaconfigured to store data such as encoded and decoded audio and videodata, or the like. Other types of tangible media includes removable harddisks, optical storage media such as CD-ROMS, DVD-ROMS, and bar codes,semiconductor memories such as flash memories, read-only-memories(ROMS), battery-backed volatile memories, networked storage devices, andthe like (825).

In the present embodiment, display driver 820 may also include softwarethat enables communications over a network such as the HTTP, TCP/IP,RTP/RTSP, and other encrypted and/or proprietary protocols, and thelike. In alternative embodiments of the present invention, othercommunications software and transfer protocols may also be used, forexample IPX, UDP or the like.

FIG. 9 is representative of a display driver 820 capable of outputtingimages for display devices 810. It will be readily apparent to one ofordinary skill in the art that many other hardware and softwareconfigurations are suitable for use with the present invention. Forexample, display driver 820 may be a personal video recorder (PVR) suchas TiVo, a cable-decoder box, a DVD-player, a Blu-ray DVD player, a HDDVD player, a notebook computer, a desk top computer, a media-centercomputer, a hand-held device (e.g., PIM, iPod, PSP), a video-tapeplayer, or the like. In still other embodiments, the techniquesdescribed below may be implemented upon a chip or an auxiliaryprocessing board (e.g., graphics processor unit).

In one embodiment of the present invention, display driver 820 is aDVD-player, and the calibration images illustrated above are stored inan encoded form into a DVD disk. The user then navigates one or moremenus of the DVD disk to have display driver 820 display calibrationimages. In this embodiment, two alternating calibration images are thendecoded from data stored on the DVD disk and then output to a displaydevice (e.g., display device 805) for the user to view. As discussedabove, certain parameters of the display device are then adjusted by theuser, based-upon viewing the two alternating calibration images, untilthe user is satisfied with the calibration of the display device. Thedisplay device is then calibrated for play-back of additional data fromthe DVD disk or other source. As detailed above, the calibration may beindependently set for the black and white levels from the gamma levels.In other embodiments, a display driver may internally store calibrationimages, as described above. These images are then retrieved and used forcalibration, independent of the DVD disk or other media.

Further embodiments can be envisioned to one of ordinary skill in theart after reading the attached documents. For example, more than twocalibration images may be displayed, increasing the amount of“animation” apparent to a viewer of the display. In other embodiments,the different calibration images may have obvious differences, such ascolored dots (e.g., black dots, white dots) at different locations(e.g., corners) on each calibration image so that the user is made awarewhen to look for differences in the black optimize regions and whitecheck regions. In still other embodiments, the two or more calibrationimages are converted into a stream of images on the display at least 30frames a second, e.g., frozen on the screen. Because the stream ofimages includes duplicate repeating images, the bit stream requirementof such embodiments is very small.

In other embodiments, combinations or sub-combinations of the abovedisclosed embodiments can be advantageously made. The block diagrams ofthe architecture and flow charts are grouped for ease of understanding.However it should be understood that combinations of blocks, additionsof new blocks, re-arrangement of blocks, and the like are contemplatedin alternative embodiments of the present invention.

The specification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense. It will, however, beevident that various modifications and changes may be made thereuntowithout departing from the broader spirit and scope of the invention asset forth in the claims.

1. A method for calibrating display device, comprising: a) determining aplurality of display portions, including at least a first displayportion and a second display portion, that can collectively define adisplay image; b) determining at least a first pattern for the firstdisplay portion and a second pattern for the second display portion; c)generating a first display image, wherein a first set of intensityvalues is mapped to the first pattern and a second set of intensityvalues is mapped to the second pattern; d) generating a second displayimage, wherein a third set of intensity values is mapped to the firstpattern and a fourth set of intensity values is mapped to the secondpattern and the third set of intensity values is different from thefirst set of intensity values; e) outputting the first display imageusing the display device, for at least a first display period; f)outputting the second display image using the display device, for atleast a second display period; g) repeating steps e) and f) for a timesufficient for a changing display to be observed by a user forcalibration purposes; and h) accepting user input reflecting userobservation of the changing display.
 2. The method of claim 1, whereinthe user input represents a request for altering at least one displayparameter that is a black-level setting, a white-level setting, acontrast setting, a brightness setting and/or a gamma setting.
 3. Themethod of claim 1, further comprising additional display images beyondtwo display images, wherein the additional display images are displayedfor additional display periods.
 4. The method of claim 1, wherein thefourth set of intensity values is equal to the second set of intensityvalues and wherein the first display period is equal to the seconddisplay period and both are equal to at least one display frame time. 5.The method of claim 1, further comprising receiving a display controlsignal indicative of a user response to a visual comparison of intensityvalues of the first region compared to intensity values of the secondregion as the display alternates among at least the first and seconddisplay images.
 6. The method of claim 1, further comprising repeatingsteps a)-h) until an indication is received that the intensities ofpixels in the first pattern substantially visually match the intensitiesof pixels in the second pattern.
 7. The method of claim 1, whereinoutputting the display image using the display device comprisesproviding an output signal to at least one of a progressive-scan CRTdisplay, a progressive-scan plasma display, a progressive-scan LCDdisplay, a progressive-scan DLP display, a projector, a reflectivescreen, and/or a transmissive screen.
 8. A display driving device,comprising: a memory configured to store a representation of positionsof at least a first display portion and a second display portion withina display image, representations of at least a first pattern for thefirst display portion and a second pattern for the second displayportion, representations of at least three sets of intensity values,comprising a first set of intensity values to be mapped to the firstpattern in a first display image, a second set of intensity values to bemapped to the second pattern in the first display image and a third setof intensity values to be mapped to the first pattern in the seconddisplay image, wherein at least the third set of intensity values isdifferent from the first set of intensity values; an output to providean electrical signal for a display device; an input to receive userinput signals; a processor coupled to the memory, the output and theinput, wherein the processor is configured to read from the memory,control the electrical signal and receive the user input signals,wherein the control of the electrical signal includes directing theoutput of the first display image to the display device for at least afirst display period, the output of the second display image to thedisplay device for at least a second display period, and repeating avarying display of at least the first display image and the seconddisplay image, until a user input signal is received or acalibration-ending signal is received; and an output for providingdisplay calibration control signals determined by the processor inresponse to the user input signals, wherein at least some of the userinput signals are interpreted by the processor as indicating userobservation of the varying display.
 9. The display driving device ofclaim 8, wherein the output to provide an electrical signal for adisplay device and the output for providing display calibration controlsignals are two outputs provided over common interface.
 10. The displaydriving device of claim 8, wherein the user input signals include userinput for adjusting visual characteristics of the display device beingdriven and the processor adjusts the sets of intensity values inresponse to such user input, to provide a calibration feedback loop. 11.The display driving device of claim 10, wherein the user inputrepresents a request for altering at least one display parameter that isa black-level setting, a white-level setting, a contrast setting, abrightness setting and/or a gamma setting.
 12. The display drivingdevice of claim 10, wherein the user input represents a display controlsignal indicative of a user response to a visual comparison of intensityvalues of the first region compared to intensity values of the secondregion as the display varies among at least the first and second displayimages.
 13. The display driving device of claim 8, further comprisingstorage for additional display images beyond two display images, whereinthe processor is configured to display the additional display images foradditional display periods and wherein a single set of intensity valuesis used for both the second set of intensity values and the fourth setof intensity values, and wherein the processor is configured to repeatthe varying display until either a user input signal or acalibration-ending signal is received and the receipt signals that auser determined that intensities of pixels in the first patternsubstantially visually match intensities of pixels in the secondpattern.
 14. The display driving device of claim 8, wherein the outputto provide an electrical signal for a display device is an outputconfigured for at least one of a progressive-scan CRT display, aprogressive-scan plasma display, a progressive-scan LCD display, aprogressive-scan DLP display, a projector, a reflective screen, and/or atransmissive screen.
 15. The display driving device of claim 8, whereinthe processor is further configured to output the first display imageand the second display image as progressive-scanned images.
 16. Acomputer program product that comprises a non-transitory tangible mediastoring computer-executable code for execution upon a computer systemincluding a processor, the computer program product comprising: codethat directs the processor to generate a first display image and asecond display image, each of the display images having logically aplurality of display portions, including at least a first displayportion and a second display portion, that can collectively define adisplay image, there being at least a first pattern for the firstdisplay portion and a second pattern for the second display portion;code that directs the processor to output the first display image, forat least a first display period, with a first set of intensity valuesmapped to the first pattern and a second set of intensity values mappedto the second pattern; code that directs the processor to output thesecond display image, for at least a second display period, with a thirdset of intensity values mapped to the first pattern and a fourth set ofintensity values mapped to the second pattern, wherein the third set ofintensity values is different from the first set of intensity values;code that directs the processor to repeat a varying display of at leastthe first display image and the second display image, until a user inputsignal is received or a calibration-ending signal is received; and codethat directs the processor to respond to user input reflecting userobservation of the varying display.
 17. The computer program product ofclaim 16, wherein the user input represents a request for altering atleast one display parameter that is a black-level setting, a white-levelsetting, a contrast setting, a brightness setting and/or a gamma settingand the code that directs the processor to respond to user inputincludes code for directing a display device to alter its at least onedisplay parameter setting.
 18. The computer program product of claim 16,further comprising code that directs the processor to output additionaldisplay images beyond two display images as part of the varying display,wherein the additional display images are displayed for additionaldisplay periods.
 19. The computer program product of claim 16, whereinthe fourth set of intensity values is equal to the second set ofintensity values, wherein the first display period is equal to thesecond display period and both are equal to at least one display frametime, and wherein the code that directs the processor to repeat thevarying display is such that the repetition continues until receipt of adisplay control signal indicative of a user response to a visualcomparison of intensity values of the first region compared to intensityvalues of the second region as the display varies among at least thefirst and second display images.
 20. The computer program product ofclaim 16, wherein the code that directs the processor to repeat thevarying display is such that the varying display can be provided as aninput to at least one of a progressive-scan CRT display, aprogressive-scan plasma display, a progressive-scan LCD display, aprogressive-scan DLP display, a projector, a reflective screen, and/or atransmissive screen.